Process for making low density foams, polyol composition and reaction system useful therefor

ABSTRACT

The invention relates to a polyol composition comprising by weight 60-97% of b1) a polyoxyethylene-polyoxypropylene polyol, having a functionality of 2-6, with 10-25% tipped EO, 3-40% of b2) a polyoxyethylene-polyoxypropylene polyol, having a functionality of 2-6, with 20-50% total EO and 10-20% tipped EO; and 0-25% of b3) a polyol, having a functionality of 2-6, with at least 50% random EO. The invention also relates to a process for preparing a flexible polyurethane foam by reacting a) a polyisocyanate composition; b) a polyol composition of the invention; c) water; and d) additives and auxiliaries known per se. The invention finally relates to a reaction system comprising A) a polyisocyanate and B) an isocyanate-reactive component comprising the polyol of the invention.

This application is the National Phase of International ApplicationPCT/EP00/04038 filed May 5, 2000, which designated the U.S. and thatInternational Application was published under PCT Article 21(2) inEnglish. The PCT application is hereby incorporated in its entirety byreference.

The instant invention relates to a process for making low density foams.It also relates to a specific polyol composition and to a reactionsystem that are useful in the said process.

For flexible polyurethane foams, low density means cost effectiveness.Thus, low density is a target, that should however not be obtained withdetrimental effects on the foam properties. Physical blowing, usingcarbon dioxide for example, is known to reduce foam density, but isassociated with processing difficulties as well as the need foradditional equipment.

U.S. Pat. No. 5,686,502 discloses foams obtained through a one-shotprocess, where the polyol comprises a first polyol which is apoly(oxyalkylene)triol which is chain terminated with oxypropylene(PO)and a second polyol which is either (i) a poly(oxyalkylene)diolterminated with EO, or (ii) a polyfunctional polyol terminated with PO.The thus obtained foams are hydrophylic. The densities obtained in theexamples vary between 13 and 20 kg/m³. There is no mention of theresilience.

U.S. Pat. No. 5,420,170 discloses foams that are visco-elastic which areprepared by reacting a specific polyol composition. The polyolcomposition comprises a block PO/EO polyol having an OH value of 14 to65, 2 to 9% of tipped EO and a functionality of 2.3 to 2.8 and a di-ortri-functional PO/EO polyol having an OH value of 20 to 80 and 60 to 85%of EO (preferably up to 20% as tipped EO). The resulting foams arevisco-elastic and do not exhibit any ball rebound (for densitiesobtained in the examples of about 70-77 kg/m³).

U.S. Pat. No. 4,833,176 discloses a process comprising reacting apolyisocyanate with a polyol at a NCO index below 70. The polyol mayvary; examples comprise mixtures of a low EO-content polyol and high EOcontent polyol.

EP-A-0 845 485 discloses a process for preparing flexible foamscomprising reacting a polyisocyanate with a polyol, where the polyol isa specific polyol composition. Said polyol composition comprises: (i) apolyetherpolyol having a functionality of 2.5-6.0, which is a PO/EOpolyol with 15% or less of EO; (ii) a polyetherpolyol having afunctionality of 1.8-2.5, which is an all-PO polyol; (iii) apolyetherpolyol having a functionality of 1.8-6.0 and having an EOcontent of at least 50 wt %. The respective amounts of components (i),(ii) and (iii) are as follows: (i) 15-70%, (ii) 30-80%, and (iii) 3-15%,based on the combined weights of the polyols.

U.S. Pat. No. 5,594,097 discloses a polyol comprising PO and EO, havingan OH value of 16-45, a primary hydroxyl content of at least 50%, an EOcontent of 21-49%, and having a structure of the type PO-(PO/EO)-EO,where the tipped EO content is 10-20%. This specific polyol is said tobe usable in combination with other polyols. All examples, however,relate to polyol compositions comprised solely of this specific polyol.Also, while a relatively low density is obtained, (i) there is nodisclosure of the resilience values and (ii) there are processingdifficulties and bad compression set when the EO-enriched polyol is usedas the main polyol.

None of the above documents teaches or suggests the instant invention.

The following way of describing polyols is used in the presentapplication: A PO-EO polyol is a polyol having first a PO block attachedto the initiator followed by an EO block. A PO-PO/EO polyol is a polyolhaving first a PO block and then a block of randomly distributed PO andEO. A PO-PO/EO-EO polyol is a polyol having first a PO block then ablock of randomly distributed PO and EO and then a block of EO. A PO-EOpolyol is a polyol having first a PO block and then an EO block. In theabove descriptions only one tail of a polyol is described (seen from theinitiator); the nominal hydroxy functionality will determine how many ofsuch tails will be present.

The present invention provides a process that surprisingly affords aresilient flexible polyurethane foam having a good stability (lowrecession) and the advantages of EO enriched polyol as the main polyol(i.e. density reduction) without having the drawbacks (i.e. negativeimpact on mechanical properties, like tensile strength, elongation andtear strength).

The invention thus provides a polyol composition comprising:

b1) a polyoxyethylene-polyoxypropylene polyol, having an average nominalhydroxyl functionality of 2-6 where the EO is present as tipped EO, theEO content being between 10-25% by weight based on the weight of thepolyol

b2) a polyoxyethylene-polyoxypropylene polyol, having an average nominalhydroxy functionality of 2-6, where the EO is present as tipped EO andrandom EO, the total EO content being between 20-50% and the tipped EOcontent being between 10-20%, both by weight based on the weight of thepolyol

b3) a polyol, having an average nominal hydroxy functionality of 2-6,and comprising EO and optionally PO where the EO is present as randomEO, the EO content being at least 50% by weight based on the weight ofthe polyol

these polyols b1, b2 and b3 being present according to the followingproportions, based on the combined weights of b1, b2 and b3, b1: 60-97wt %, b2: 3-40 wt %, b3: 0-25 wt %.

Unless otherwise stated amounts of EO and PO in a polyol are indicatedhereinafter as % by weight based on the weight of the polyol.

The invention thus provides a process for preparing a flexiblepolyurethane foam at an NCO index of 70-120 and preferably of 70-105 byreacting

a) a polyisocyanate;

b1) a polyoxyethylene-polyoxypropylene polyol, having an average nominalhydroxyl functionality of 2-6 where the EO is present as tipped EO, theEO content being between 10-25%;

b2) a polyoxyethylene-polyoxypropylene polyol, having an average nominalhydroxy functionality of 2-6, where the EO is present as tipped EO andrandom EO, the total EO content being between 20-50%, the tipped EOcontent being between 10-20%,

b3) a polyol, having an average nominal hydroxy functionality of 2-6,and comprising EO and optionally PO where the EO is present as randomEO, the EO content being at least 50%,

these polyols b1, b2 and b3 being present according to the followingproportions, based on the combined weights of b1, b2 and b3, b1: 60-97wt %, b2: 3-40 wt %, b3: 0-25 wt %;

c) water; and

d) additives and auxiliaries known per se.

The invention finally relates to a reaction system comprising A) apolyisocyanate and B) an isocyanate-reactive component comprising thepolyol of the invention and water, as well as to a reaction systemcomprising A) a polyisocyanate prepolymer obtained by reacting thepolyisocyanate with part of the polyol composition of the invention, andB) an isocyanate-reactive component comprising the remainder of thepolyol composition of the invention and water.

In the context of the present invention the following terms, if andwhenever they are used, have the following meaning:

1) isocyanate index or NCO index:

the ratio of NCO-groups over isocyanate-reactive hydrogen atoms presentin a formulation, given as a percentage$\frac{\lbrack{NCO}\rbrack \times 100}{\left\lbrack {{active}\quad {hydrogen}} \right\rbrack}(\%)$

In other words the NCO-index expresses the percentage of isocyanateactually used in a formulation with respect to the amount of isocyanatetheoretically required for reacting with the amount ofisocyanate-reactive hydrogen used in a formulation.

It should be observed that the isocyanate index as used herein isconsidered from the point of view of the actual foaming processinvolving the isocyanate ingredient and the isocyanate-reactiveingredients. Any isocyanate groups consumed in a preliminary step toproduce modified polyisocyanates (including such isocyanate-derivativesreferred to in the art as quasi or semi-prepolymers and prepolymers) orany active hydrogens reacted with isocyanate to produce modified polyolsor polyamines, are not taken into account in the calculation of theisocyanate index. Only the free isocyanate groups and the freeisocyanate-reactive hydrogens (including those of the water, if used)present at the actual foaming stage are taken into account.

2) The expression “isocyanate-reactive hydrogen atoms” as used hereinfor the purpose of calculating the isocyanate index refers to the totalof hydroxyl and amine hydrogen atoms present in the reactivecompositions in the form of polyols, polyamines and/or water; this meansthat for the purpose of calculating the isocyanate index at the actualfoaming process one hydroxyl group is considered to comprise onereactive hydrogen, one primary or secondary amine group is considered tocomprise one reactive hydrogen and one water molecule is considered tocomprise two active hydrogens.

3) Reaction system: a combination of components wherein thepolyisocyanate component is kept in a container separate from theisocyanate-reactive components.

4) The expression “polyurethane foam” as used herein generally refers tocellular products as obtained by reacting polyisocyanates withisocyanate-reactive hydrogen containing compounds, using foaming agents,and in particular includes cellular products obtained with water asreactive foaming agent (involving a reaction of water with isocyanategroups yielding urea linkages and carbon dioxide and producingpolyurea-urethane foams).

5) The term “average nominal hydroxyl functionality” is used herein toindicate the average functionality (number of hydroxyl groups permolecule) of the polyol composition on the assumption that this is theaverage functionality (number of active hydrogen atoms per molecule) ofthe initiator(s) used in their preparation although in practice it willoften be somewhat less because of some terminal unsaturation.

6) The term “average” is used to indicate an average by number. Thepolyisocyanates may be selected from aliphatic, cycloaliphatic andaraliphatic polyisocyanates, especially diisocyanates, likehexamethylene diisocyanate, isophorone diisocyanate, cyclohexane-1,4-diisocyanate, 4,4′-dicyclohexylmethane diisocyanate and m-andp-tetramethylxylylene diisocyanate, and in particular aromaticpolyisocyanates like tolylene diisocyanates (TDI), phenylenediisocyanates and most preferably diphenylmethane diisocyanateoptionally comprising homologues thereof having an isocyanatefunctionality of 3 or more (such diisocyanates comprising suchhomologues are known as crude MDI or polymeric MDI or mixtures of suchcrude or polymeric MDI with MDI) and modified variants thereof.

The diphenylmethane diisocyanate (MDI) used may be selected from4,4′-MDI, 2,4′-MDI, isomeric mixtures of 4,4′-MDI and 2,4′-MDI and lessthan 10% by weight of 2,2′-MDI, and modified variants thereof containingcarbodiimide, uretonimine, isocyanurate, urethane, allophanate, ureaand/or biuret groups. Preferred are 4,4′-MDI, isomeric mixtures of4,4′-MDI and 2,4′-MDI and less than 10% by weight of 2,2′ MDI anduretonimine and/or carbodiimide modified MDI having an NCO content of atleast 20% by weight and preferably at least 25% by weight and urethanemodified MDI obtained by reacting excess MDI and polyol having amolecular weight of at most 1000 and having an NCO content of at least20% by weight and preferably at least 25% by weight.

Diphenylmethane diisocyanate comprising homologues having an isoycanatefunctionality of 3 or more are so-called polymeric or crude MDI.

Polymeric or crude MDI are well known in the art. They are made by thephosgenation of a mixture of polyamines obtained by the acidcondensation of aniline and formaldehyde.

The manufacture of both the polyamine mixtures and the polyisocyanatemixtures is well known. The condensation of aniline with formaldehyde inthe presence of strong acids such as hydrochloric acid gives a reactionproduct containing diaminodiphenylmethane together with polymethylenepolyphenylene polyamines of higher functionality, the precisecomposition depending in known manner inter alia on theaniline/formaldehyde ratio. The polyisocyanates are made by phosgenationof the polyamine mixtures and the various proportions of diamines,triamines and higher polyamines give rise to related proportions ofdiisocyanates, triisocyanates and higher polyisocyanates. The relativeproportions of diisocyanate, triisocyanate and higher polyisoycanates insuch crude or polymeric MDI compositions determine the averagefunctionality of the compositions, that is the average number ofisocyanate groups per molecule. By varying the proportions of startingmaterials, the averace functionality of the polysiocyanate compositionscan be varied from little more than 2 to 3 or even higher. In practice,however, the average isocyanate functionality preferably ranges from2.3-2.8. The NCO value of such polymeric or crude MDI is at least 30% byweight. The polymeric or crude MDI contain diphenylmethane diisocyanate,the remainder being polymethylene polyphenylene polyisocyanates offunctionality greater than two together with by-products formed in themanufacture of such polyisocyanates by phosgenation of polyamines.Further modified variants of such crude or polymeric MDI may be used aswell comprising carbodiimide, uretonimine, isocyanurate, urethane,allophanate, urea and/or biuret groups; especially the aforementioneduretonimine and/or carbodiimide modified ones and the urethane modifiedones are preferred. Mixtures of polyisocyanates may be used as well.

The invention also relates to a polyol composition, comprised of polyolsb1, b2 and b3.

Polyol b1 can be prepared by known methods. It has a structure of thetype PO-EO, where EO is present as tipped EO. The EO content is from 10to 25% by weight.

Polyol b2 can also be prepared by known methods. It can have a structureof the type PO-PO/EO-EO or of the type PO/EO-EO. EO is present as tippedand random. The total EO content is from 20 to 50% by weight, preferablyfrom 21 to 49%, the tipped EO content is from 10-20% by weight. In thePO-PO/EO-EO type polyol, the first PO block comprises preferably from 20to 75% by weight of the PO units. Preferably the weight ratio tippedEO/random EO is from 1:3 to 3:1. The polyol having a structure of thetype PO-PO/EO-EO can notably be produced according to the teaching ofU.S. Pat. No. 5594097. The polyol having a structure of the type-PO/EO-EO can notably be produced according to the teaching of U.S. Pat.No. 4559366.

Polyol b3 is the optional polyol. It can also be prepared by knownmethods. It can have a structure of type PO/EO or of the type -EO (PEG).EO is present as random EO (if and when PO is present). The EQ contentis more than 50% by weight. Preferably it is a polyoxyethylene polyol.The functionality of these polyols is comprised between 2 and 6,preferably between 2 and 4.

For b1 and b2, the equivalent weight is generally comprised between 1000and 4000, preferably 1500 and 3500; while for b3, the equivalent weightis generally comprised between 200 and 3000, preferably 300 and 2000.

The polyol composition comprises the various polyols according to thefollowing proportions, expressed on the basis of the combined weights ofthe polyols:

b1: 60-97%, preferably 65-90%

b2: 3-40%, preferably 10-30%

b3: 0-25%, preferably 0-10% (more preferably 3-10%); all percentagesbeing % by weight.

Each component b1, b2 and b3 may be comprised of mixtures.

Dispersed material can also be present. This is known aspolymer-modified polyol, and comprise e.g. SAN or PIPA (Poly IsocyanatePoly Addition).

The polymer-modified polyols which are particularly interesting inaccordance with the invention are products obtained by in situpolymerisation of styrene and/or acrylonitrile inpoly(oxyethylene/oxypropylene)polyols and products obtained by in situreaction between a polyisocyanate and an amino-or hydroxy-functionalcompound (such as triethanolamine) in apoly(oxyethylene/oxypropylene)polyol. The solids content (based on thetotal polyol weight b1+b2+b3) can vary within broad limits, e.g. from 5to 50% by weight. Particle sizes of the dispersed polymer of less than50 microns are preferred. Mixtures can be used as well.

Water is used as the blowing agent. Carbon dioxide may be added ifneeded. In the case of highly resilient water blown flexible foams, itis appropriate to use from 1.0 to 15 and preferably from 2 to 10% byweight of water based on the weight of the total polyol component wherethe water can optionally be used in conjunction with carbon dioxide.

Other conventional ingredients (additives and/or auxiliaries) may beused in making the polyurethanes. These include catalysts, for example,tertiary amines and organic tin compounds, surfactants, cross linking orchain extending agents, for example, low molecular weight compounds suchas diols, triols (having a molecular weight below the one of b3) anddiamines, flame proofing agents, for example halogenated alkylphosphates, fillers and pigments. Foam stabilizers, for examplepolysiloxane-polyalkylene oxide block copolymers, may be used tostabilize or regulate the cells of the foam.

The amount of these minor ingredients used will depend on the nature ofthe product required and may be varied within limits well known to apolyurethane foam technologist.

The present invention also relates to a process for preparing a flexiblepolyurethane foam at an NCO index of 70-120 by reacting a polyisocyanatea); a polyoxyethylene-polyoxypropylene polyol b1); apolyoxyethylene-polyoxypropylene polyol b2); a polyol b3); according toratios specified above; water c); and additives and auxiliaries knownper se d).

These components, notably the polyols b1, b2 and b3 can be added in anyorder. Notably, the polyols can be added according to the followingnon-limiting possibilities:

Part of b1+b2+b3, then the remainder of b1+b2+b3;

Part of b1+b2 but no b3, then the remainder of b1+b2 and all b3;

Part of b1+b3 but no b2, then the remainder of b1+b3 and all b2;

all of b1, then the all of b2+b3; all of b2, then the all of b1+b3;

Part of b1, then the remainder of b1 together with the all of b2+b3;

Part of b2, then the remainder of b2 together with the all of b1+b3;

And any other possibility.

In the process of the invention, it is to be noted that one shot,prepolymer or quasi-prepolymer methods may thus be employed as may beappropriate for the particular type of polyurethane being made. Thecomponents of the polyurethane forming reaction mixture may be mixedtogether in any convenient manner, for example the individual componentsmay be pre-blended so as to reduce the number of component streams to bebrought together in the final mixing step. It is often convenient tohave a two-stream system whereby one stream comprises a polyisocyanateor isocyanate-terminated prepolymer and the second stream comprises allthe other components of the reaction mixture.

The flexible foams may be made according to techniques known in the artlike the moulding or the slabstock technique. The foams may be used inthe furniture and automotive industries in seating, cushioning andmattresses.

The flexible foams thus obtained have a free rise density comprisedbetween 18 and 60 kg/m³. These foams show a resilience higher than 45%.

The following examples illustrate the invention without limiting same.

Unless otherwise indicated, all parts are given by weight.

Glossary

(All Functionalities are Nominal Functionalities, equivalent weichts arenominal equivalent weights, all % are % by weight and OH values are inmg KOH/g)

Polyol A PO-EO, with EO as tipped. EO content is 15%. Equivalent weightis 2004. Functionality is 3, OH value is 28.

Polyol B PO-PO/EO-EO, total EO content is 21%. Tip EO content is 15%.Equivalent weight is 2004. Functionality is 3, OH value is 28.

Polyol C PO-PO/EO-EO, total EO content is 28,6%. Tip EO content is 15%.Equivalent weight is 2004. Functionality is 3, OH value is 28.

Polyol D PO/EO-EO, total EO content is 26%. Tip EO content is 15.Equivalent weight is 2158. Functionality is 3, OH value is 26.

Polyol E PO/EO-EO, total EO content is 21%. Tip EO content is 15%.Equivalent weight is 1934. Functionality is 3, OH value is 29.

Polyol F polyoxyethylene polyol having an equivalent weight of 450, anOH value of 123 and a functionality of 3.

Polyol G Polymer polyol, comprising 25% of dispersed particulate SANmaterial in high molecular weight polyol, similar to polyol A, but withan equivalent weight of 1600 and an OH value of 35.

Polyol H PO/EO-EO, total EO content is 28%. Tip EO content is 15%.Equivalent weight is 2004. Functionality is 3, OH value is 28. Primaryhydroxyl content is 85.2

Polyol I PO-PO/EO-EO, total EO content is 28%. First PO block contains55% PO over total PO and EO. Tip EO content is 15%. Equivalent weight is2004. Functionality is 3, OH value is 29. Primary hydroxyl content is86.7

Isocyanate A MDI comprising 93.8% diisocyanate 48.2% of which is2,4′-MDI and 6.2% is oligomer species of higher functionality.Functionality is 2.05.

Isocvanate B MDI comprising 87.5% diisocyanate 46.0% of which is2,4′-MDI and 12.5% is oligomer species of higher functionality.Functionality is 2.10.

Isocyanate C Quasi-prepolymer based on MDI (81.3% diisocyanate 30% ofwhich is 2,4′-MDI and 18.7% is oligomer species of higher functionality,Functionality is 2.16.) and polyol A. NCO value is 29.7.

Isocyanate D MDI comprising 78.2% diisocyanate 26.0% of which is2,4′-MDI and 21.8% is oligomer species of higher functionality.Functionality is 2.19.

D8154 Amine catalyst from Air Products

Niax Al Catalyst from Union Carbide

D33LV Catalyst from Air Products

DMEA Dimethylethanolamine

DETDA diethyl toluenediamine

Foams are produced according to the following scheme. Polyols,catalysts, surfactants, water are mixed prior to the addition ofisocyanates. Polyol blends and isoyanates are mixed at 20° C. during 8seconds before foaming. Free-rise foams are made in plastic buckets of2.5 1 to 10 1. Moulded foams are made with a square mould of 9.11preheated to 45° C.

The properties of the foam are determined according to the followingmethods and standards FRD (Free Rise Density);

OAD (OverAll Density) (kg/cm³), and CD (Core Density) (kg/cm³): ISO 845Compression hardness; CLD 40% (kPa) and Hysteresis Loss (%): ISO 3386-1Compression set (thickness): Dry 75% (%) and Humid 75% (%): ISO 1856Indentation Hardness: ILD 40% (N) and Hysteresis Loss (%): ISO 2439Resilience (%) Toyota Tear strength, max (N/rn): ISO 8067 Tensilestrength(kpa) and Elongation (%): ISO 1798

The results are summarized in the following tables. From the last table,one will note that the specific polyols of the type PO/EO-EO are evenbetter than those of the type PO-PO/EO-EO, since they provide higherfoam stability (lower recession %) and lower free rise density, and arethus particularly designed for making lower density foams.

Examples Component 1 2 3 4 5 6 7 8 9 10 11 12 Polyol A 75 65 65 75 85 8565 60 85 75 75 65 Polyol B 20 30 30 20 Polyol C 10 10 30 35 10 20 20 30Polyol D Polyol E Polyol F 5 5 5 5 5 5 5 5 5 5 5 5 Polyol G Water 6.56.5 6 6 5 5 6 6 5 6 7 8 B 4113 0.8 0.8 1.2 1.2 0.5 1.0 1.0 1.0 1.0 1.01.0 1.0 D 8154 0.7 0.7 0.6 0.6 0.7 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Niax A10.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 0.1 D 33 LV 0.3 0.3 0.3 0.3 0.30.3 0.3 0.3 0.3 0.3 0.3 DMEA 0.5 DETDA 0.3 Isocyanate A 80 80 75 85 85Isocyanate B 80 80 75 85 85 100 Isocyanate C 76 NCO index 80 80 86 86 8589 85.6 85.6 96 86.4 80 82.2 Examples Component 13 14 15 16 17 18 19 2021 22 23 24 Polyol A 65 65 65 65 85 85 67 67 55 65 55 55 Polyol B 30 3030 30 30 Polyol C 10 10 8 8 Polyol D 10 20 Polyol E 20 Polyol F 5 5 5 55 5 5 5 5 5 5 5 Polyol G 20 20 15 20 20 20 Water 6 6 7 7 5 5 4 5 6.6 4 44 B 4113 1.2 1.2 1.2 1.2 1.2 1.2 0.5 0.5 1.2 0.5 0.5 0.5 D 8154 0.6 0.60.6 0.6 0.6 0.6 0.7 0.7 0.6 0.7 0.7 0.7 Niax A1 0.1 0.1 0.1 0.1 0.1 0.10.1 D 33 LV 0.3 0.3 0.3 0.3 0.3 0.3 0.3 DMEA 0.5 0.5 0.5 0.5 0.5 DETDA0.3 0.3 0.3 0.3 0.3 Isocyanate A Isocyanate B 75 80 80 85 75 80 85Isocyanate C 63 76 63 63 63 NCO index 80 86 74 79 96 101 86 86 83.5 8686 86 Examples Properties 1 2 3 4 5 6 7 8 9 10 11 12 Cells open openopen* Open* open open open open open* open* open open Recession % 8 4 00 2 5 5 2 0 0 0 2 FRD (kg/cm³) 26.7 23.3 22 22.8 33.5 27.7 24.6 23.525.5 19.6 21.2 19.6 Moulding overall density kg/m³) Core density (kg/m³)Compression hardness CLD 40% (kPa) 1.7 3.25 2.8 2.8 2.7 1.7 2.3 2.2 3.2Hysteresis (%) 34.3 35.05 34 39.3 42.7 31.35 39.5 42.4 46.5 Compressionset (thick) Dry 75% (%) Humid 75% (%) Indentation hardness ILD 40% (N)Hysteresis (%) Resilience (%) 55.4 48.2 Tear strength Max (N/m) Tensilestrength (kPa) Elongation (%) Examples Properties 13 14 15 16 17 18 1920 21 22 23 24 Cells open* open* open* open* open* open* Open OpenRecession % 0 0 0 0 0 0 0 0 FRD (kg/cm³) 39 34.5 22.8 Moulding overalldensity (kg/m³) 42.9 44.2 43.9 44.8 Core density (kg/m³) 21.1 20.2 20.219.1 22.3 22.3 41 42.4 41.1 41.7 Compression hardness CLD 40% (kPa) 1.41.6 1.5 1.6 1.5 1.9 3.7 4.6 2.7 4.6 5.0 4.6 Hysteresis (%) 3.0 31.9 32.434.5 26.1 30.4 26.9 40.6 42.9 28.7 28.4 28.4 Compression set (thick) Dry75% (%) 12.4 11.6 18.9 25.6 7 7.5 10.1 8.7 9.1 8.5 Humid 75% (%) 25.636.5 49.9 53 13.3 12.5 12.8 10.6 9.4 9.4 Indentation hardness ILD 40%(N) 211.8 255 264 267 Hysteresis (%) 28.2 30.9 31.7 30.7 Resilience (%)51.5 51 50 50 56 53.5 55.4 54.6 54.9 54.2 Tear strength Max (N/m) 205219 225 248 175 169 190 246 249 246 Tensile strength (kPa) 70 81 80 8478 83 87.2 85 79 84 Elongation (%) 135 117 123 115 108 105 90 97 97 95Example Component 25 26 27 28 29 30 Polyol A 90 85 80 90 85 80 Polyol H10 15 20 Polyol I 10 15 20 Water 4.2 4.2 4.2 4.2 4.2 4.2 B 4113 0.8 0.80.8 0.8 0.8 0.8 Niax A1 0.1 0.1 0.1 0.1 0.1 0.1 D 33 LV 0.8 0.8 0.8 0.80.8 0.8 Isocyanate D 60 60 60 60 60 60 NCO index 89 89 89 89 89 89 Cellsopen open open open open open Recession % 22 16 5 27 20 10 FRD (kg/cm³)50.5 43.8 36.3 55.9 47.9 37.8 Compression hardness CLD 40% (kPa) 7.0 6.05.1 7.3 6.4 5.1 Hysteresis (%) 33.9 35.7 39.6 34.1 35.0 37.7 *borderline

What is claimed is:
 1. A polyol composition comprising: b1) apolyoxyethylene-polyoxypropylene polyol, having an average nominalhydroxyl functionality of 2-6 where the EO is present as tipped EO, theEO content being between 10-25%; b2) a polyoxyethylene-polyoxypropylenepolyol, having an average nominal hydroxy functionality of 2-6, wherethe EO is present as tipped EO and random EO, the total EO content beingbetween 20-50%, the tipped EO content being between 10-20%, b3) apolyol, having an average nominal hydroxy functionality of 2-6, andcomprising EO and optionally PO where the EO is present as random EO,the EO content being at least 50%, these polyols b1, b2 and b3 beingpresent according to the following proportions, based on the combinedweights of b1, b2 and b3, b1: 60-97 wt %, b2: 3-40 wt %, b3: 0-25 wt %.2. The polyol composition according to claim 1, which comprises thepolyols b1, b2 and b3 according to the following proportions: b1: 65-90wt %, b2: 10-30 wt %, b3: 0-10 wt %.
 3. The polyol composition accordingto claim 1, in which the polyoxyethylene-polyoxypropylene polyol b2),the weight ratio tipped EO/random EO is between 1:3-3:1.
 4. The polyolcomposition according to claim 1, wherein the polyol b2) is of the-PO-PO/EO-EO type.
 5. The polyol composition of claim 1, wherein thepolyol b2) is of the-PO/EO-EO type.
 6. The polyol composition of claim1, wherein the functionality if the polyol b1, b2 and b3 is 2-4.
 7. Thepolyol composition of claim 1, wherein the polyol b3) is apolyoxyethylene polyol.
 8. The polyol composition of claim 1, whichcomprises dispersed particles.
 9. The polyol composition of claim 1,wherein the equivalent weight of polyols b1) and b2) is 1000-4000 and ofpolyol b3) is 200-3000.
 10. Process for preparing a flexiblepolyurethane foam at an NCO index of 70-120 by reacting a) apolyisocyanate composition; b1) a polyoxyethylene-polyoxypropylenepolyol, having an average nominal hydroxyl functionality of 2-6 wherethe EO is present as tipped EO, the EO content being between 10-25%; b2)a polyoxyethylene-polyoxypropylene polyol, having an average nominalhydroxy functionality of 2-6, where the EO is present as tipped EO andrandom EO, the total EO content being between 20-50%, the tipped EOcontent being between 10-20%, b3) a polyol, having an average nominalhydroxy functionality of 2-6, and comprising EO and optionally PO wherethe EO is present as random EO, the EO content being at least 50%, thesepolyols b1, b2 and b3 being present according to the followingproportions, based on the combined weights of b1, b2 and b3, b1: 60-97wt %, b2: 3-40 wt %, b3: 0-25 wt %; c) water; and d) additives andauxiliaries known per se.
 11. The process according to claim 10, inwhich the polyols b1, b2 and b3 are used according to the followingproportions: b1: 65-90 wt %, b2: 10-30 wt %, b3: 0-10 wt %.
 12. Theprocess according to claim 10, in which thepolyoxyethylene-polyoxypropylene polyol b2), the weight ratio tippedEO/random EO is between 1:3-3:1.
 13. The process of claim 10, whereinthe polyol b2) is of the -PO-PO/EO-EO type.
 14. The process compositionof claim 10, wherein the polyol b2) is of the-PO/EO-EO type.
 15. Theprocess of claim 10, wherein the functionality of the polyols b1, b2 andb3 is 2-4.
 16. The process of claim 10, wherein the polyol b3) is apolyoxyethylene polyol.
 17. The process of claim 10, in which the polyolcomprises dispersed particles.
 18. The process of claim 10 whereinpolyols b1) and b2) have an equivalent weight of 1000-4000 and polyolb3) of 200-3000 and polyisocyanate is diphenylmethane diisocyanateoptionally comprising homologues thereof having an isocyanantefunctionality of 3 or more modified variants thereof.
 19. A reactionsystem comprising A) a polyisocyanate and B) an isocyanate-reactivecomponent comprising the polyol composition of claim 1 and water.